<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        *{margin: 0;padding: 0}
        input,button{
            width: 200px;
            height: 30px;
            border: 1px solid #333;
            padding: 5px;
        }
        button{
            box-sizing: content-box;
        }
        /* button box-sizing:border-box 给边框和填充不会改变它的width,height */
    </style>
</head>
<body>
   <input type="text"><br>
   <button>btn</button>
</body>
</html>